Field of the Invention
The present invention relates to a wireless LAN system, and more specifically, a frame transmission/reception method by a station operating in a power save mode in a wireless LAN system and an apparatus supporting the same.
Related Art
With the growth of information communication technology, various wireless communication technologies have been recently developed. Among others, wireless LAN (Local Area Network) is a technology that allows for wireless access to the Internet at home or business or in a specific service area using a handheld terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc.
IEEE 802.11n is a technology standard that has been recently established in order to overcome the limit to communication speed that has been recognized as a weakness of wireless LAN. IEEE 802.11n aims to increase network speed and reliability and expand coverage of a wireless network. More specifically, the IEEE 802.11n system adopts MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both a transmission unit and a reception unit thereof so as to optimize data speed and to minimize transmission errors while supporting a high throughput (HT) of data processing speed up to 540 Mbps.
In the wireless LAN system, a station (STA) supports a power save mode. The station may prevent unnecessary power consumption by entering into a doze state. In case there is traffic associated with data that intends to be sent to an STA that is operating in a doze state, an access point (AP) may notify this to the STA. The STA recognizes existence of traffic associated with data intended to be sent thereto and may request that the AP be sending it to the STA. The AP may transmit a frame in response to the STA's request.
Meanwhile, if the AP may transmit only one frame in response to the request from the STA that has entered into an awake state, it may be inefficient in view of traffic processing. Further, the STA shifts between the awake state and doze state more frequently, and thus efficiency may be deteriorated in terms of power saving operation. Accordingly, a need exists for a frame transmission and reception method that may enhance power save mode efficiency of an STA and good traffic processing.